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trailer wiring


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bmata1980 
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Posted: August 22, 2013 at 12:19 AM / IP Logged  
I have a car hauler with a 9000 lb winch that will pull 480 amps max. I have a 7 prong connector on my truck that has a battery wire (hot when ignition on). Now if I want to keep the truck running as I winch something up on the trailer, the load will fry the wire as it is a small gauge. Now I hear that what I need is a battery isolator. I do not want the heavy draw of amps to affect the vehicle wiring however I need to have about 10 amps available to charge the trailer battery. I hope someone can understand this and help. Thanx
bmata1980 
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Posted: August 22, 2013 at 12:20 AM / IP Logged  
P.S. My truck is a 98 F-150
oldspark 
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Posted: August 22, 2013 at 2:23 AM / IP Logged  
Your battery will probably take far more than 10A when recharging, at least initially.
And if you are running the truck whilst winching, your battery interconnection must handle over 500A (max winch current plus battery recharge current).
What batteries are you running in the trailer?
bmata1980 
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Posted: August 22, 2013 at 10:08 AM / IP Logged  
The battery for the winch is a 500 cold cranking amps deep cycle marine battery. The truck came with 7 prong tow connection from the factory. The wire is a small gauge, definitely not a large gauge battery cable. Im sure it was meant to charge the battery. It just cannot handle a large amperage. (100+). effectively I need something with a resistor in line to reduce the amps but also something that will allow for enough amps to charge the the batt (20-30amps)
oldspark 
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Posted: August 22, 2013 at 10:25 AM / IP Logged  
The cable might be sufficient to charge the battery, but not with the engine AND winch running.
Not that IMO that "hot when ignition on" wire was intended for a 2nd battery, but if it was, I'm sure a battery isolator would have been included. (And it seems a battery isolator is not fitted.)
I'd suggest a self resetting circuit breaker else circuit breaker at each end of the battery link to suit the interlink cable capacity.
But a 500CCA battery might not be enough for a 450A winch if used for more a minute or so - not if you want the battery to last.
You really need to determine how much you expect to draw, how long for, and then match battery capacity (AH) to that and limit battery discharge to ~50% for a deep cycle (80% for a cranking battery) for reasonable battery life. Of course "emergency" winching at the expense of battery life may be acceptable to you.
Forget resistors. A current limiter maybe, but hence the circuit breakers.
Phreak480 
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Posted: August 22, 2013 at 12:42 PM / IP Logged  
What you really should do is add a separate connector that can handle the current. Anderson power pole connectors are a good choice. Then you can have the benefit of running the engine when winching.
oldspark 
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Posted: August 22, 2013 at 6:59 PM / IP Logged  
Phreak480 is right, and the Andersons handle both poles (+12V power and ground) tho their largest is the SB350 which is (only) rated for 350A, but that might not be a major issue in practice. (You'd use much heavier than 400A rated cable - maybe 500A etc - and be prepared for the SB350 to be a point of failure unless you used 350A breakers etc.)
Phreak480 
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Posted: August 22, 2013 at 9:09 PM / IP Logged  
Oldspark is right but in reality that is the rating for constant draw, not peak spikes. Your constant draw in all likelihood will be under the 350 amps even though you may peak higher.
They use the anderson powerpoles on forklift batteries and use them for unpluggable jumper cables and they get used for winches mounted to vehicle hitches to make them removable all the time. Most of the winch manufacturers have quick disconnect wiring kits based on teh anderson powerpole plug.
bmata1980 
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Posted: August 22, 2013 at 9:23 PM / IP Logged  
Thanx very much for all the help. I think the route of running a separate set of large gauge wires and anderson connectors strictly for the battery and winch is the best practical idea.
oldspark 
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Posted: August 22, 2013 at 11:02 PM / IP Logged  
Just to augment... Yet again Phreak480 is correct (about the 350A & peak loads etc).
And that's what I meant by "in practice".
There are so many aspects to a design like this...
What is the stalled current of the winch? (Is it higher than its "rated" 480A?)
Do you allow for the 2nd battery not supplying any current?
Ditto, but also taking a recharge current?
The latter should be abnormal and handled by protection (fuses/breakers), but often designs are done to those "specs".
However when approaching economically practical limits like being limited to the 350A Anderson, "reality" is desirable.
With equally charged batteries and interconnect resistance, the main/front battery won't supply as much as half the current.
However, with the engine running AND assuming the alternator can handle the winch loading, the full winch current will go thru the Anderson, plus 2nd battery charge current (a mere ~2A if its full).
But since you probably don't have a 350A etc alternator, in simple theory the full alternator output plus whatever current is required from the front battery will go thru the link & Anderson.
In brief, it's unlikely that the Anderson will see 350A even under heavy winching.
And if that is exceeded, protection should handle that (fuses/breakers sized for the lesser of the Anderson or cable).

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